Process of making sulphite liquor



June l2, H923.,

G. A. RICHTER PROCESS OF MAKING SRULPHITE. LlQU-OR Filed Sept. 3, 1920 MAK ESQ 2SC. kob

Fatented .lune i12, 11323. A

GEORGE A. RICHTER, 0F OF BERLIN,

ras

literarias BERLIN,

new HAMPSHIRE, Assrenoa 'ro Bao comma,

NEW ,c MPSHIRE, A CORPORATION 0F MAINE. ,f

' PROCESS 0F MAKING SULPHITE LIQUOE.

.applic To all whom it may concern:

Be it known that I, (iconen States, in the county of Coos and State of citizen of the United Berlin,

A. RICHTER, a residing at New Hampshire, have invented new and useful Improvements in Processes of Making Sulphite Liquor, of which the following is a specification.

The object of the present inventionist'o provide a method for the recovery and utilization of sulphur dioxide issuing from those liquors from the relief digesters which are used for the cooking of the raw material in the manufacture of sull The accompanying ihite pulp.

drawing illustrates more or less conventionally a system for the making of raw acid liquor (e. g. calcium bisulphite) and an apparatus for the rccovcry of sulphur dioxide from the relief liquor and its introduction liquor system.

One of the purposes,

into the raw acid for which thc invention is particularly intendcd,`is to so utilize the sulphur dioxide recovered from the relief liquor that it shall not have the effect of diluting the free SO2 c. ished cooking acid liquor, duced into the acid liquo and also to assist in the cooking liquor rich in ontent of the finwhen it is intror-making system, production of a free SO., without the refrigeration of the liquor used for absorbing or combining with the l have shown a relief pipes 3 and 4 leadin portion of the digester and connected vby a 5, and a separator 6 for separating gas from the liquor.

coupling the relief digester 1, below pit 2,

g from the upper The two pipes 3 and 4, which are, as usual, screened (not shown) at their inlets to prevent the entrance of pulp, are provided with the valves 7 and 8 as ordinar shown conventionally a which serves as a part of At 9 I have direct condenser a recovery system ily.

(forming no part of the present invention) by which sulphur dioxide is recovered from the blow pit vapors and shown the various conne'cti gases.

I have not ons by which acid liquor and steam are introduced into the digester, as these are all well known and may be of common construction. The system, as it may be termed for producing the raw acidliquor,comprises'ftwo towers 10, 11,

which form a part, and in which sulphur dioxide is absorbed 'and combined to form what may be termed a ra w calcium bisulation led September 3, 1920. Serial No. 408,052.

ll2 and 13, supported by perforated partitions 14, 15. Cooled' and purified sul hurburner gases are introduced into the ower end of tower 10 by a pipe or conduit 16, leading from the cooling apparatus by which the hot burner gases are cooled and more or less purified. These gases are caused to pass through the absorption towers 10, 11, in series, by a pipe 17 leading from the upper portion of tower 10 to the lower portion of tower 11. The tail gases from tower 11 are wasted through the outlet pipe 18. Water introduced into tower 11 by pipe 19, valved as at 20, is caused to flow in counter current to the flow of the gases through the towers in series, being pumped by a pump 21 from the bottom of tower 11 to the top of tower 1() through the intermediate lconnecting pipe 22, which has a regulating valve 23. 'These parts constitute one form of what l herein refer to as a system for producing the raw sulphite solution.

There is a third tower (the finishing or relief tower) 24, in which the raw bisulphite liquor is enriched with free sulphur dioxide gas, from the digester relief liquor, and which for the purpose contains a mass of inert interstitial surface material 25 (e. g. spiral brick, fragments of field rock or their equivalent), supported on a perforated partition 26. The raw acid liquor (calcium bisulphite) from the tower 10 is forced by pump 27 through pipe 28, having a regulating valve 29 to the top of tower 24, and the relief gas from the separator 6 is conducted by pipe 30 to the bottom of tower 24. The pipe 30 passes through a suitable cooler 31,

and has a regulating valve 32. rlhe tail gas system isgemployed to treat the liot relief rich burner gas,I but to ybe commingledor liquor delivered by the separator l6 and to mixed with gas of an approximately l-ike free vit from its uncombined SU, content, strength and recirculated through the second andA the tail gas thus enriched is recircutower 11 of the series. The waste relief liqlated through a ortion of the rawf acid uor from the recovery tower, under proper 70 liquor'system. is forms an important regulation, contains ordinarily only from i\ feature of the present invention. As shown, 0.2% to total SO2, so that the loss of iff-employ a recovery tank or tower 38, havsulphur is reduced to the minimum. Fui'- ing a perforatedfpartition 39 on which is tliermore, by tlievuse of tail gas for the relllsupported a mass of inert interstitial surface covery of free S()2 from thc-relief liquor, 75

material 40 (such as hereinbcfore described), the small percentare -vof oxygen therein (it and the relief liquor is conducted from the consisting principii ly of inert gas-nitrogen) separator by a pipe 41 (valved as at 42) to av prevents oxidation of the free S()2 in the spray nozzle or distributer in the top of relief liquor. I should not consider it a dethe tower. A fan 43'is employed to force parture from the spirit and scope of my in- 80 a portion of the tail gas from the exit convention if the S()2 were recovered from the duit 18 of tower 11 tothe bottom of the rerelief liquor by any other method, and decovcry tank or tower 38 so as to flow through livered to the acid system at some portion the mass of inertmaterial in direct contact thereof which corresponds to anequilibrium 20 with and in counter direction to the flow of, determined by the concentration of S92 in 85 relief liquor therethrough to sweep the free the gas leaving the recovery tower. Ac- ,S02 therefrom. The enriched tail gas is cording to the process as herein rdescribed, conducted by a pipe 441 (having a valve 45)` thel raw sulphite liquor from the tower 10 from the top of the recovery tower 38, tothe contains about 2.5% free and,1.2%' combined raw acid liquor system, its delivery end be- SO2, and, in the final or finished acid tower 90 I ing` shown as connectedto the gas conduit 24, the resultant acid liquor has ,a content 17, between the towers 11 and 10, so that of about ,5% free and 1% to 1.2% combined it will bel commingled and mixed with the SO2. The tail gas from thelast-mentioncd unabsorbed gases iowing from tower '10 to tower 24 has a content of about 20% to 40% tower 11. The relief liquor, which has been SO2, and this, as'previously stated, is com- 95 substantially freed from uneombined SO2,^ min led with the burner gas and recircu. is conducted from the recovery tower 38 latecgithrourh the absorption towers whereinl by a trap ed pipe 46 valved as at 47 a the -raw suliihite liquor is produced;

n sin ex anation .of the process which is The process as hereinbeforel described practice by aid of the 'apparatusl `thus depossessesthe additional advantages z- 100 scribed, I may state, first, that it is m obv First.-By preventing the dilution of tin- 'ect to secure a finished acid liquorhavlng a ished cooking acid liquor by a relatively igh content, say 5%,0f free sulphllrous acid, large volume (30%) of warm dilute relief 4 and to Secure an economy of operation byI acid liquor, it allows 'the manufacture, under V proximately 1% to 4% SO2. The relief liqrial.

tent approximately 90% to 100% SO2.

no nitrogen and a small proportion '(say 3%) quently, the usual elaborate lead cooling` ap- I ca 0 utilizing uncombined S02 found in the sepasuirimer conditions, of a cookin acid liquor 105 rated relief liquor in enriching,r tail gas from containing as high as 5% free i O2, without l the raw acid liquor, and to deliver such enr very .material loss of sulphur contained in `riched gas to the raw acid liquor at a point the extracted hot relief liquor,

where the unabsorbed burner gas is of ap- Secondfv-By freeing the hot relief liquor proximately the same strength inSOz.. The of available sulphur dioxide, I am able to UU cooled burner gas delivered through pipe 16' discard ligneous products resulting'` from has a content of approximately 18% SO2, the cooking operation, and hence the cookwhereas the unabsorbed gases, passing from ing acid liquor'will always be clean and free the absorption tower 10, has a content of apfrom appreciable amounts of organic niatcl l 5 uor from separator 6, at a temperature of Third-In the ordinary acid liquor proabout 210 F., contains about 0.2% comducingir system, wherein a relief separator is bined and 0.3% to 1.0% free S02, whereas employed, it is necessary to install an elabothe relief gas fom the separator has a conrate cooling system forl the hot corrosive relief liquor. AIn the apparatus herein de- In the present process, the tail gas from scribed, inasmuch as the relief liquor is dethe absorption towers, which contains little livcred as a waste product from the bottom or no free SO2 and consists principally of of towei- 38, itI need n'ot be cooled. Consoof oxygen, is conducted throu h the recovery .paratus can be eliminated. towerf38, where it is enriched y the recovery What I claim iszof free SO2 from the' relief liquor, to a 1. A process of making sulphite cooking goint where it contains from 1.0%,to 4.0% liquor, which comprises producingr a sul- 0 and it is returned to the raw acid liquor phitc solution by an absorption system, sep- Ain such manner as notto dilute the relatively arating the gases from the hot liquor re- 13 Messie lieved from the digester, cooling the strong gas thus separated, absorbing sulphur dioxide from the cooled strong gas, recovering free sulphur dioxide from the remaining hot relief liquor, and passing such recovered sulphur dioxide into the said system where the strength ofthe gas in said system is approximately that of the recovered gas.

2. A process of making sulphite cooking liquor, which comprises producing a sulphite solution byan absorption system, recovering uncombined sulphur dioxide gas from relief liquor delivered from 'the digester by passing tail gas from the said system through the relief liquor.

3. A process of making sulphite'cooking liquor, which comprises producing a sulphite solution by an absorption system, recovering uncombined sulphur dioxide gas from relief liquor delivered from the digester by circulating tail gas from the said system through the relief liquor, and passing such enriched tail gas back to the said system at a point where the gas in the system has approximately the samesulphur dioxide content as the enriched tail gas.

4. A process of making sulphite cooking liquor, which comprises producing a sulphite solution by an absorption system, separating the gases from the hot liquor relieved from the digester, cooling the strong gas thus separated, absorbing sulphur dii oxide from the cooled strong gas, recovering free sulphur dioxide from the remaining hot relief liquor, by passing tail gas from the said system through such relief li uor, and passing the enriched tail gas bac to the said system at a point Where the gas in the system has approximately the same sulphur dioxide content as the enriched tail gas.

5. A process of making sulphite cooking liquor having a high content of free sulphur dioxide, which comprises producing the sulphite solution by an absorption system, separating the gases from the hot liquor relieved from the digester, cooling the strong gas thus separated, recovering free sulphur dioxide from the remaining hot relief liquor and passing it into the absorption system at a point Where the gas therein has approximately the same sulphur dioxide content, and enriching the sulphite liquor from the absorption system by causing it to absorb the cooled strong relief gas.

6. A process of making sulphite cooking liquor having a high content of free sulphur dioxide, which comprises producing a su1. phite solution by an absorption system, separating the gases from the hot liquor relieved from the digester, cooling the strong gas thus separated, recovering free sulphur dioxide from the remaining hot relief liquor and assing it into the absorption system at a point Where the gas therein hasl approximately the same sulphur dioxide content, enriching the sulphite liquor from the absorption system by causing it to absorb the cooled strong gas, and passing such of said gas as is not absorbed. back into the absorption system.

lin testimony whereof ll have laed my signature.

GEORGE A. RECHTER. 

